BILBAO, Spain — Kylian Mbappe said he will take full responsibility for his "big mistake", after the striker missed another penalty in Real Madrid's 2-1 defeat to Athletic Bilbao in La Liga on Wednesday.

A week after the French superstar failed from the spot in the Champions League against Liverpool, he endured further misery from 12 yards as Los Blancos allowed league leader Barcelona to retain its four-point advantage.

Alejandro Berenguer fired Bilbao ahead early in the second half, with Jude Bellingham leveling for Madrid after Mbappe's penalty miss.

However, substitute Gorka Guruzeta snatched victory for fourth-placed Athletic in the 80th minute, after taking advantage of a Fede Valverde error.

The defeat, and Mbappe's penalty miss, will heap further pressure on to the former Paris Saint-Germain striker, after plenty of criticism in recent weeks.

"A big mistake in a match where every detail counts. I take full responsibility for it," said Mbappe in a post on social media platform Instagram.

"A difficult moment, but it's the best time to change this situation and show who I am."

Madrid coach Carlo Ancelotti said the forward was downhearted after goalkeeper Julen Agirrezabala saved his penalty.

"Obviously (Mbappe) is sad, disappointed, but he has to continue," the Italian told reporters.

Mbappe has scored 10 goals in his first 20 games for Madrid across all competitions, but is struggling for consistency.

"He's not at his best level, but we have to give him time to adapt, he's scored 10 goals, he can do better and he's working to do that," said Ancelotti.

Madrid was hoping to build on three consecutive wins in La Liga, despite missing Vinicius Junior and other injured stars, with Ancelotti bringing French midfielder Aurelien Tchouameni back into the starting lineup.

Thibaut Courtois made an important early intervention to deny Spain winger Nico Williams, with his brother Inaki Williams lurking dangerously.

It was a first half of few clear chances, but one played with intensity in front of a packed San Mames stadium.

Mbappe found the net, but the goal was ruled out for offside. The referee also reviewed a Rodrygo penalty appeal, but decided the Brazilian winger went down too easily.

At the other end, Berenguer should have put the host ahead, but blasted high over the bar after Inaki Williams' clever backheel teed him up.

The forward made amends early in the second half by bundling home from close range, after Courtois could only palm an Inaki Williams cross into his path.

'Incredible night'

Mbappe had the chance to put the reigning champion back on level terms, when Agirrezabala barreled into Antonio Rudiger and the referee awarded a penalty.

After missing from the spot against Liverpool, Mbappe agreed to let Bellingham take a penalty against Getafe on Sunday.

However, this time, the French forward stepped up himself, but his weak effort, again to the goalkeeper's left, was at a comfortable height for Agirrezabala to parry.

"These days we study everything a lot, I knew he was a good penalty taker, and he'd missed the last one. I thought he would go the same way, and, luckily, he did," Agirrezabala told DAZN.

"I'm very happy for what was an incredible night, beating Real Madrid in front of our fans is so nice."

Mbappe did play a part in Madrid's equalizer, though, with a vicious drive from distance that the stopper could only push out and back into the path of Bellingham, who finished tidily for his fourth goal in his last four league games.

Madrid was only level for two minutes before Bilbao regained the lead through Guruzeta, who stole the ball as Valverde prepared to pass and fired low past Courtois.

Mbappe cut a deflated figure in the final stages, with one attempt to break down the left quickly shut down by the Bilbao defense, eliciting raucous cheers from their jubilant supporters.

Last season, Real Madrid lost just twice across all competitions on its way to a La Liga and Champions League double, but this was its fifth defeat of the current campaign.

"Bit by bit, we will get players back (from injury) and we will improve our level," pledged Ancelotti.

AFP